By Jill on Thursday, August 19, 1999 - 11:13 am:
Hi I am getting a "humplike" peak in a pure sample of methanol. This peak only shows up around 230nm. I am using a PDA detector, and Waters instruments. Mobile Phase is 55:45 methanol, .0425% Phosphoric acid. column novapak phenyl 100x5mm, flow =.75ml.min
THings I have tried:
1.Injecting mobile phase samples to see if they are contaminated.
2.Flushing column with 100% water for few hours
3.Flushing column with 100% methanol for few hours
4.Changing column to a nova pak C18
5.Preparing new mobile phase
6.Sonicated reservoir inlet filters
Pull hair out
By B.Buglio on Thursday, August 19, 1999 - 12:32 pm:
A couple of questions to start with:
Whats the retention time of the hump?
Are you premixing solvents or letting the chromatograph do the mixing?
By Jill on Thursday, August 19, 1999 - 01:27 pm:
The retention time is 3.00min. It's an isocratic run with the instrument doing the mixing.
By B.Buglio on Saturday, August 21, 1999 - 02:42 pm:
What happens when you run with a premixed the mobile phase?
By Jill on Tuesday, August 24, 1999 - 01:17 pm:
I ran a premixed mobile phase which did not make a difference.
By Jill on Wednesday, August 25, 1999 - 12:29 pm:
Hi I have attached chromatograms showing blank methanols and a sample.
[Note from Moderator: To download these files using Internet Explorer, right click on the file name. In the dialog box, select "Save Target As...". In the Save As box, change the file extension from "unk" to ".cdf" (for example, change "285_peaka2774_cdf.unk" to "285_peaka2774.cdf". Click Save.]
 DIPeak3299.cdfdipeak3299.cdf (3 k) |
| PeakA2774.cdf peaka2774.cdf (3 k) |
| PeakB2985.cdf peak_b2985.cdf (3 k) |
By Anonymous on Friday, October 22, 1999 - 01:00 pm:
Try running a low conc. sample of HCHO Formaldehyde. It mat be were your ghost peak is originating from
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